Fish farm technology. 1 - Brackishwater fish culture based on "aquafeed"

A method has been evolved to enhance the production of natural feed in brackish water fish farms by providing substrates for bio-growth ('aquafeed' production) which is a biomass complex consisting of sedentary and associated organisms of plant and animal species. The seasonal fluctuations of the aquafeed production over different substrates ranged as: 787-1830g/coconut leaf (6m²)/45 days, 16.0-072.9g/glass panel (2x10x10cm²)/30 days, 52-230g/nylon mat (2x25x25cm²)/30 days and 18.6-123.1g/wooden block (6x10x10cm²)/30 days. The average dry weight composition of the major components of aquafeed obtained in the present study was sand-silt-clay 40%, protein 22%, carbohydrate (water soluble) 1.8% and fat 3.35% (water content 85%). Mugil cephalus of 1.85 cm reared in a 0.01ha pond and fed on aquafeed attained a size of 23 cm length and 146.73g weight during one year. Survival rate was 54% at a density of 1000/ha. Salinity and temperature of the pond during the culture period ranged between 1.4 and 32.8‰ and 28.1 and 36.5°C respectively.

Frozen storage studies of composite fish mince drom dhooma (Sciaenid sp.) and lactarius (Lactarius lactarius)

Fish minces from dhoma and lactarius were mixed in the ratio of 40:60 respectively, and quick frozen along with individual minces at -40°C and stored at -20°C. Shelf life was evaluated by following biochemical, physical and organoleptic changes occurred during storage up to 44 weeks. Rapid decreases were noted in water soluble nitrogen and salt soluble nitrogen fractions during the initial period of 16 weeks. A good correlation was observed between changes in salt-soluble nitrogen and organoleptic evaluation. The minces were in good and acceptable condition up to 32 weeks of storage.

Comparison of sensory characteristics and biochemical parameters in commercial frozen prawns

Commercial samples of frozen shrimp of different styles of presentation and size grades were tested for sensory, physical (cooked yield and pH) and biochemical characteristics (moisture, total nitrogen, water extractable nitrogen, nonprotein nitrogen, alpha amino nitrogen, total volatile nitrogen and trimethylamine nitrogen). The test results are compared and correlated. The order of preference of the samples were HL>PUD>P & D. There was significant correlation between sensory score of cooked sample and WEN, NPN and ∞ – NHsub(2)-N values. TVN and TMA-N did not exhibit any correlation with sensory score. It is inferred that in quality measurement of frozen shrimps of commerce the quantity of water soluble components and the total dry matter can be used to support the sensory test results.

Studies on iced storage of cultured rohu (Labeo rohita)

The biochemical, bacteriological and organoleptic changes in cultured rohu (Labeo rohita) during iced storage have been studied. Non-protein nitrogen decreased and water soluble nitrogen remained almost same during storage in ice. Initially, when the fish was in pre-rigor and rigor conditions, the extractability of protein was low (45 to 50%) which increased after the resolution of the rigor and the decrease in extractability towards the end of storage was insignificant. The total volatile base nitrogen remained steady up to 7 days in ice and showed slight decrease on further storage. During iced storage the bacterial count increased from 10^3/g to 10^5/g by the 11th day of storage. Nearly 80-90% of the total bacterial population in fresh fish was constituted by mesophiles which decreased gradually (decreased to 1% by 13th day of iced storage). Organoleptically the fish was acceptable up to 15 days in ice.

Comparison of physicochemical properties of muscle proteins in cultured and wild prawns (Penaeus (Fenneropenaeus) orientalis Kishinouye, 1918)

Protein physicochemical properties in cultured and wild prawns (Penaeus (F.) orientalis Kishinouye, 1918) were studied and compared. Protein fractions were separated into water-soluble, salt-soluble, alkali-soluble, and stroma. The results showed that salt- and alkali-soluble proteins were slightly higher in wild prawns and water-soluble proteins were higher in cultured prawns. There were only slight differences in Ca super(2+)-ATPase, MG super(2+)-ATPase, and ATP sensitivities. The textural values of wild prawns were significantly higher than the cultured ones.

Application of gel-casting to the fabrication of 1-3 piezoelectric ceramic-polymer composites for high-frequency ultrasound devices

A modified gel-casting technique was used to fabricate a 1-3 piezoelectric ceramic/polymer composite substrate formed by irregular-shaped pillar arrays of small dimensions and kerfs. This technique involves the polymerization of aqueous piezoelectric (PZT) suspensions with added water-soluble epoxy resin and polyamine-based hardener that lead to high strength, high density and resilient ceramic bodies. Soft micromoulding was used to shape the ceramic segments, and micropillars with lateral features down to 4 m and height-to-width aspect ratios of ∼10 were achieved. The composite exhibited a clear thickness resonance mode at approximately 70 MHz and a k eff ∼ 0.51, demonstrating that the ceramic micropillars possess good electrical properties. Furthermore, gel-casting allows the fabrication of ceramic structures with non-conventional shapes; hence, device design is not limited by the standard fabrication methods. This is of particular benefit for high-frequency transducers where the critical design dimensions are reduced. © 2012 IOP Publishing Ltd.

Cytochemical changes in the developmental process of Nostoc sphaeroides (cyanobacterium)

There are several apparent developmental stages in the life cycle of Nostoc sphaeroides Kutzing, an edible cyanobacterium found mainly in paddy fields in central China. The cytochemical changes in developmental stages such as hormogonia, aseriate stage, filamentous stage and colony in N. sphaeroides were examined using fluorescent staining and colorimetric methods. The staining of acidic and sulfated polysaccharides increased with development when hormogonia were used as the starting point. Acidic polysaccharides (AP) were most abundant at the aseriate stage and then decreased, while the sulfated polysaccharides (SP) were highest at the colony stage. Quantitatively, along the developmental process from hormogonia to colony, total carbohydrates first increased, then became stable, and then reached their highest level at the colony stage, while reducing sugars were highest at the hormogonia stage and then decreased sharply once development began. SP were not detectable in the hot water soluble polysaccharides (HWSP), and hormogonia had the lowest content of AP, while old colonies had the highest. The AP content of the aseriate stage, filamentous stage and young colony stage were very similar. The evolutionary relationships reflected in the developmental stages of N. sphaeroides are discussed.

Effects of gibberellin A(3) on growth and microcystin production in Microcystis aeruginosa (cyanophyta)

Environmental. factors that affect the growth and microcystin production of microcystis have received worldwide attention because of the hazards microcystin poses to environmental safety and public health. Nevertheless, the effects of organic anthropogenic pollution on microcystis are rarely discussed. Gibberellin A(3) (GA(3)) is a vegetable hormone widely used in agriculture and horticulture that can contaminate water as an anthropogenic pollutant. Because of its common occurrence, we studied the effects of GA3 on growth and microcystin production of Microcystis aeruginosa (M. aeruginosa) PCC7806 with different concentrations (0.001-25mg/L) in batch culture. The control was obtained without gibberellin under the same culture conditions. Growth, estimated by dry weight and cell number, increased after the GA3 treatment. GA3 increased the amounts of chlorophyll a, phycocyanin and cellular-soluble protein in the cells of M. aeruginosa PCC7806, but decreased the accumulation of water-soluble carbohydrates. In addition, GA3 was observed to affect nitrogen absorption of the test algae, but to have no effect on the absorption of phosphorus. The amount of microcystin measured by enzyme-Linked immunosorbent assay (ELISA) increased in GA3 treatment groups, but the stimulatory effects were different in different culture phases. It is suggested that GA3 increases M. aeruginosa growth by stimulating its absorbance of nitrogen and increasing its ability to use carbohydrates, accordingly increasing cellular pigments and thus finally inducing accumulation of protein and microcystin. (C) 2007 Elsevier GmbH. All rights reserved.

Effects of salt stress on carbohydrate metabolism in desert soil alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra- and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+-ATPase.

Studies on polysaccharides from three edible species of Nostoc (Cyanobacteria) with different colony morphologies: Comparison of monosaccharide compositions and viscosities of polysaccharides from field colonies and suspension cultures

Hot water-soluble polysaccharides woe extracted from field colonies and suspension cultures of Nostoc commune Vaucher, Nostoc flagelliforme Berkeley et Curtis, and Nostoc sphaeroides Kutzing. Excreted extracellular polymeric substances (EPS) were isolated from the media in which the suspension cultures were grown. The main monosaccharides of the field colony polysaccharides from the three species were glucose, xylose, and galactose, with an approximate ratio of 2:1:1. Mannose was also present, but the levels varied among the species, and arabinose appeared only in N. flagelliforme. The compositions of the cellular polysaccharides and EPS from suspension cultures were more complicated than those of the field samples and varied among the different species. The polysaccharides from the cultures of N. flagelliforme had a relatively simple composition consisting of mannose, galactose, glucose, and glucuronic acid, but no xylose, as was found in the field colony polysaccharides. The polysaccharides from cultures of N. sphaeroides contained glucose (the major component), rhamnose, fucose, xylose, mannose, and galactose. These same sugars were present in the polysaccharides from cultures of N. commune, with xylose as the major component. Combined nitrogen in the media had no qualitative influence on the compositions of the cellular polysaccharides but affected those of the EPS of N. commune and N. flagelliforme. The EPS of N. sphaeroides had a very low fetal carbohydrate content and thus was not considered to be polysaccharide in nature. The field colony polysaccharides could be separated by anion exchange chromatography into neutral and acidic fractions having similar sugar compositions. Preliminary linkage analysis showed that 1) xylose, glucose, and galactose were 1-->4 linked, 2) mannose, galactose, and xylose occurred as terminal residues, and 3) branch points occurred in glucose as 1-->3,4 and 1-->3,6 linkages and in xylose as a 1-->3,4 linkage. The polymer preparations from field colonies had higher kinematic viscosities than those from corresponding suspension cultures. The high viscosities of the polymers suggested that they might DE suitable for industrial uses.

黄土高原长期种植苜蓿对土壤硫、钙、镁的影响

以22年定位试验为基础,研究黄土高原长期种植紫花苜蓿(Medicago sativaL.)情况下土壤硫、钙、镁组分的变化。结果表明:长期施P使苜蓿连作耕层土壤总硫、有效硫、水溶性硫、吸附性硫、HCl可溶性硫、总无机硫和有机硫含量分别增加9.41%、62.41%、47.51%、30.07%、2.25%、5.38%和17.54%;长期施NPM使苜蓿连作耕层土壤总硫、有效硫、水溶性硫、吸附性硫、HCl可溶性硫、总无机硫和有机硫含量分别增加20.89%、98.31%、68.44%、57.34%、8.07%、12.54%和37.69%。长期施P使苜蓿连作耕层土壤全钙、有效钙、水溶态钙、交换态钙和酸溶态钙含量增加分别增加4.64%、4.27%、11.66%、4.05%和8.59%,但残余态钙含量降低2.21%;长期施NPM使苜蓿连作耕层土壤全钙、有效钙、水溶态钙、交换态钙和酸溶态钙含量增加分别增加8.69%、8.30%、51.59%、6.73%和27.77%,但残余态钙含量降低26.23%。长期施NPM使苜蓿连作耕层土壤全镁、有效镁、水溶态镁、交换态镁、酸溶态镁和残余态镁含量分别增加7.38%、61.98%、63.16%...

黄土高原旱区长期施肥条件下土壤钾素形态空间分布特征及有效性研究

在黄土高原南部旱地长期肥料定位试验的基础上研究了土壤钾素空间分布特征及其有效性。结果表明:长期施肥后土壤中特殊吸附性钾(SAK)和非特殊吸附性钾(NSAK)储量增加,但水溶性钾(WSK)和非交换性钾(NEK)则有明显的下降,单施N水溶性钾下降了48.24%,单施P下降32.32%,NP配施和NPK配施分别下降10.61%和17.93%,非交换性钾降幅为8.56%~24.91%。增施钾肥可以缓解因长期施肥作物生长所携出的钾素,增加耕层土壤中的水溶性钾、非特殊吸附性钾及特殊吸附性钾。相关分析结果表明,土壤不同形态钾素对速效钾的重要性依次为WSK>NSAK>SAK>NEK,土壤速效钾与水溶性钾、非特殊吸附性钾呈显著相关,与特殊吸附性钾和非交换性钾无显著相关性。

次生植被下土壤活性有机碳组分季节动态研究

为了揭示不同类型植被下土壤有机碳及其活性组分季节动态变化及其特点，探讨不同的植被恢复模式对土壤有机碳组分的影响，分析影响土壤有机碳组分变化的因素，评估土壤有机活性有机碳组分参数在植被恢复过程中土壤质量监测的可靠性，为植被恢复及低效林改造技术提供理论依据。本研究选择岷江上游大沟流域的几种人工林（云杉林、油松林、华山松林、日本落叶松林）以及次生落叶阔叶灌丛下土壤，通过剖面机械分层取样，测定土壤总有机碳（TOC）和三种活性碳组分微生物碳（SMBC）、水溶性碳（WSOC）、易氧化碳（EOC）等来反映土壤变化特点。主要结果是： 1. 土壤有机碳含量平均在15.48~25.46 g kg-1之间在5月份时含量最低，随生长季的开始，有机碳含量逐渐增加，到9月份时含量达到最大值；由于新形成的凋落物不能被迅速分解利用补充土壤碳库，而原有碳库经历一个生长季的分解利用，因此，生长季末期即11月份的含量较小；土壤微生物碳含量平均在132.78~476.73mg kg-1之间，9月份和11月份含量都比较高；水溶性碳在生长季中逐步增大，含量在51.95~77.18 mg kg-1之间，到11月份时达到最大值；土壤易氧化碳平均含量在3.74~5.79g kg-1之间，含量最低值出现在5月份，但和其他碳组分不同的是其在7月份时含量较高。 2. 土壤有机碳及其活性碳组分大小关系为：TOC>EOC >SMBC>WSOC；比值约为300：70：5：1。 3. 土壤不同层次间比较，土壤碳指标都表现为随土壤深度增加而逐渐减小, 表层积聚作用明显。 4. 对土壤总有机碳量与活性碳组分以及活性碳之间进行了相关分析表明，土壤总有机碳含量与土壤微生物量碳、水溶性碳、易氧化碳之间的相关性均达到显著水平（P<0.05），有机碳总贮量很大程度上制约着土壤活性碳组分。土壤微生物量碳、水溶性碳、易氧化碳两两之间也都存在着显著相关关系（P<0.05），并随着不同植被类型或立地条件因子发生变化而变化。 5. 土壤有机碳及其活性组分与土壤养分状况之间的相关性分析发现，随着海拔、坡向或者植被类型的改变，其林下土壤有机碳及其活性组分与土壤养分的相关性也发生较大的变化。总体而言，岷江上游地区海拔、坡向、土壤自然含水量、植被盖度、凋落物厚度、土壤全N对次生林下土壤有机碳及其组分有重要影响。而AP、AK、C/N对土壤碳变化变化影响较小。 6. 通过不同海拔、坡向以及植被类型之间的综合比较分析发现，土壤微生物碳SMBC和水溶性碳WSOC比TOC和EOC更能敏感地反映出比较敏感的指示林下土壤质量的变化。 In order to reveal seasonal dynamics of soil labile organic carbon under different secondary vegetation, to analyze effect of different vegetation restoration pattern on soil organic carbon and its fractions, and to find the factors influencing changes in soil organic carbon and its fractions, further to estimate those parameters reliability for soil quality monitoring in the process of vegetation restoration. Soils were selected from several plantations, including Picea asperata Pinus tabulaeformis, Pinus armandii and Larix kaempferi and secondary shrub in Dagou Watershed of the upper reach of Minjiang River. The measurement of TOC, SMBC，WSOC and EOC were made, because these parameters can reflect change of soil characteristics. The major results are: 1. There were the lowest soil organic carbon and its labile fractions contents in May. At the time of growth initiation, they increased gradually and reached maximum in September. After that the soil organic carbon content decreased. Because current litter couldn’t be rapidly decomposed, and supplemented into carbon pool, while intrinsic carbon pool experienced decomposition and utilization of growth season, Which led a decrease in soil organic carbon content in November. Average value was 15.48~25.46 g kg-1; average SMBC content was 132.78~476.73mg kg-1.There were higher SMBC content in September and November as compared with other times; Water soluble organic carbon content increased from 51.95 mg kg-1 in May to 77.18 mg kg-1 in November; EOC content was lowest in May y. Average value was 3.74~5.79g kg-1. Differeing from other parameters of carbon fractions, EOC content was higher in July. 2. The content of soil organic carbon and its labile carbon fractions ranked as follows：TOC>EOC >SMBC>WSO，and ratio was about 300：70：5：1. 3. Consider as soil different layers，all of the parameters decreased gradually with increasing soil depth, thus displayed a significant accumulation in the surface layer soil. 4. Correlations coefficient analysis revealed that, TOC significantly correlated with SMBC, WSOC and EOC indicating total storage of organic carbon limited soil labile carbon fractions in great extent. On the other hand, there were significant correlations between SMBC，WSOC and EOC. But these relationships changed with vegetation types and/or environmental conditions. 5. The relationships between soil organic carbon and its labile fractions and soil nutrient traits changed with altitude，slope aspect and vegetations. Therefore our results suggested that altitude，slope aspect，soil natural water content，vegetation coverage, litter thickness and soil total nitrogen play a important role change in soil organic carbon and its fractions in upper reaches of Minjiang River. While AP、AK、C/N slightly influenced soil carbon. 6. Our results, on the other hand suggested that SMBC and WSOC are more sensitive to the change of altitudes, slope aspects, vegetation types than TOC and EOC, thus two parameters may be good index reflecting change of soil quality. These results provide insights into theoretical and technological evidences for the vegetation regeneration restoration and improvement of low-quality and benefit forest in the upper reaches of Minjiang River regions.

水分梯度上不同灌木生长对干旱河谷土壤理化和生物学性质的影响

岷江上游干旱河谷区水土流失强烈，地质灾害频繁，生态环境十分脆弱，而土壤条件恶劣（水分不足和养分缺乏）是阻碍该区植被恢复的关键因子，因此研究水分和乡土灌木生长对土壤的影响对该区的生态恢复具有指导意义。本文通过定点模拟实验，选取三种优势豆科灌木为研究对象，分别是白刺花（Sophora davidii）、小马鞍羊蹄甲（Bauhinia faberi var. microphylla）和小雀花（Campylotropics polyantha），设置5 个水分梯度，分别为100%、80%、60%、40%和20%田间持水量（FC），对栽种植物与不种植物下土壤理化性质和酶活性进行测定分析，系统比较和研究了不同水分条件和不同乡土灌木生长对干旱河谷区土壤结构、养分循环、酶活性以及微生物量的影响。主要结果如下：1. 无论生长植物与否，土壤的毛管持水量和毛管孔隙度都随着水分含量的减少而降低，最大持水量、总孔隙度和容重变化不大，相应地，土壤中的非毛管孔隙随含水量的减少而升高。各水分条件下，种植植物的毛管持水量和毛管孔隙度低于无植物生长的土壤，非毛管孔隙度相应地高于无植物土壤。土壤含水量在100%－40% FC 时，三种豆科灌木的毛管持水量和毛管孔隙度存在差异，而20% FC 条件下，三种豆科灌木土壤的物理性质基本相同。2. 水分胁迫影响土壤中养分的矿化和积累，主要表现在降低了水溶性碳和铵态氮的含量，中等程度胁迫时（60% FC）促进了有机碳和硝态氮的富集，对速效钾和有效磷没有明显作用。种植豆科灌木后各水分梯度上都增加了有机碳、铵态氮、速效钾和有效磷的积累。增加程度上三种豆科灌木间有一定差异，对于土壤有机碳总量，种植白刺花和小马鞍羊蹄甲明显高于小雀花，同样的情况还出现在铵态氮和速效钾上，但是对于有效磷，种植小雀花后的增加程度则明显高于白刺花和小马鞍羊蹄甲。种植豆科灌木不仅增加了土壤养分的相对含量，也改变了其在水分梯度上的变化趋势及其变化幅度，这种作用主要体现在碳元素和氮元素上。3. 无植物生长时脲酶活性随水分含量的减少而升高，水分胁迫对磷酸酶和过氧化氢酶的作用不显著，蔗糖酶也保持在相对较高的水平。种植植物后，蔗糖酶、磷酸酶活性与无植物时相比有较大幅度的提高，种植白刺花的脲酶活性也升高，其升高的程度在不同水分含量时不同。种植植物还降低了酶活性在水分梯度上的变幅，使之在水分梯度间的差异显著性降低。脲酶活性在指示土壤性质改变方面是较敏感的指标，其它三种酶在不同植物间的差异不明显。4. 在无植物生长时，中等程度的水分胁迫（60% FC）提高了土壤微生物量碳含量，过高或过低的土壤水分均不利于微生物碳的积累。种植小马鞍羊蹄甲后微生物量碳在水分梯度上的变化趋势与无植物生长时一致，而种植白刺花和小雀花后微生物量碳随着水分含量的减少而降低。不同种类植物的微生物量碳在水分梯度上的变化特征也不同，100% FC 条件下三种植物间没有差异，80%和60% FC 条件下小马鞍羊蹄甲显著高于白刺花和小雀花，40%和20% FC 条件下白刺花和小马鞍羊蹄甲也显著高于小雀花，说明不同种类植物随着干旱胁迫程度的加深微生物量碳的降低幅度不同，在极度干旱时，白刺花和小马鞍羊蹄甲土壤依然保持了较高的微生物活性，而小雀花土壤微生物量则明显下降。The dry valley of the upper reaches of the Minjiang River is seriously degradedmountain ecosystem. It was endangered by extremely soil lost and frequentlygeological disaster. Previous studies showed that short of water and nutrients in soilwas the principal limiting factors of vegetation restoration in this area. The typical soiland three dominant leguminous shrubs Sophora davidii, Bauhinia faberi var.microphylla and Campylotropics polyantha in upper reaches of arid Minjiang Rivervalley were considered as experimental material. Two-month old seedlings of eachspecies were exposed to five water supplies (100%, 80%, 60%, 40% and 20% waterfield capacity (FC)) in a temperature and light-controlled greenhouse. Afterthree-month water treatment, soil physiochemical variables and soil microbialactivities were determined by conventional methods. The main results showed that:1. Soil capillary capacity and capillary porosity decreased along water supplyregimes in all treatments, while saturated water capacity, total porosity and bulkdensity kept in a relatively stable level, as a result, the non-capillary porosity andcapacity increased with decrease of water supply. Compared to non-planted soil, theplant-soil systems had a higher non-capillary porosity and capacity, suggestingappropriate oxygen was present in soil to maintain the living of microorganism. Soilof three type shrub species shared the same capillary capacity and capillary porosityunder 20% FC.2. Water soluble carbon and NH4+-N decreased in response to water stress, whiletotal organic carbon and NO3--N promoted by moderate water stress and inhibited by 100% and 20% FC. Total organic carbon, NH4+-N, rapidly available K and availableP increased after the planting of leguminous shrubs in five water supply regimescompared to non-planted soil. For TOC, NH4+-N and rapidly available K, thepromotion effect was higher in S. davidii and B. faberi var. microphylla than C.polyantha planted soil, while available P displayed the opposite side. The planting ofshrubs also reduced the variance of observed traits along water supply gradients.3. Drought stress increased urease activity in non-planted soil, while insignificantdifferences were observed in phosphatase and catalase activity among five watersupply regimes. The planting of leguminous shrubs facilitated the β-glucosidase andphosphatase activity compared to the non-planted soil. It also reduced the variance ofenzyme activity along water supply gradients. Urease was more sensitive to waterstress than other three enzymes.4. Soil water content significantly affected microbial biomass carbon andCmic:Corg. S. davidii and B. faberi var. microphylla showed more drought toleranceability than C. polyantha, attributing not only to their relatively smaller variance ofmicrobial biomass carbon along soil water supply gradients, but also to the highlevel of microbial activity under severe water stress. S. davidii and B. faberi var.microphylla benefited reproduction of soil microorganism at 60%-80% FC, whilesevere drought limited it due to the competition of water and nutrients between plantand soil microorganism.

生姜化感作用机理及其栽培模式研究

近年来，随着对作物重茬（连年种植）障碍原因的深入研究，植物的化感作用越来越受到国内外众多学者的重视。而作为重要调料和药用植物的生姜，其连作障碍也备受关注，系统地研究生姜化感作用将有助于理解和最终解决生姜连作障碍问题。本文通过研究生姜不同部位、不同浓度的水浸液对与其间作的两个物种（大豆和四季葱）种子的萌发及幼苗生长的影响，从而证明生姜化感作用的存在；并通过温室盆栽实验研究了生姜的自毒作用（即研究生姜不同部位、不同浓度的水浸液对其幼苗的形态、生理生化、光合作用、土壤酶、土壤微生物多样性及土壤养分的影响），从而揭示生姜退化和衰老的机制，并为生姜筛选出合适的间作物种提供科学依据，对生姜连作障碍提出科学的解决方法。主要研究结果如下： 1. 与对照相比，生姜所有部位（根茎、茎、叶）、所有浓度（10、20、40、 80 g l-1）的水浸液均抑制了大豆种子和葱籽的萌发率、幼苗生长、水分吸收和脂肪酶活性，并且其抑制程度随着水浸液浓度的增加而增强，其生姜各部位水浸液抑制效应的强弱顺序为茎＞叶＞根茎。这一结果表明生姜根茎、茎、叶含有能够抑制大豆种子和葱籽种子萌发和幼苗生长的水溶性化感物质。根茎是生姜的主要收获部位，而生姜的残株（主要是茎和叶）应该从大田中处理掉以减轻其抑制效应。生姜水浸液中主要化感成分包括：根茎水浸液中主要是丁香酸和伞花内脂；茎水浸液中主要是阿魏酸，且其含量最高为73.4 ug/g；叶水浸液中除了阿魏酸，其他六种物质均检测出来，但含量较高的主要有丁香酸、伞花内脂和香豆酸。 2. 生姜茎和叶不同浓度的水浸液均显著抑制了生姜幼苗的株高、每株叶片数和叶面积，其抑制程度随着水浸液浓度的增加而有所增强，而生姜幼苗每株分枝数差异不显著；同时生姜水浸液也极大程度地影响了生姜幼苗的生物量（包括地下生物量、地上生物量和总生物量，均为鲜重）。在同一浓度下，茎水浸液对生姜幼苗形态指标及生物量指标均显示出最强的抑制作用，叶水浸液次之，根茎水浸液最弱。与对照相比，低浓度的生姜根茎水浸液提高了生姜幼苗叶片内四种抗氧化酶（SOD、POD、CAT、APX）活性，高浓度的根茎水浸液抑制了四种抗氧化酶活性，而茎和叶水浸液均随着浓度的增加而抑制了四种抗氧化酶活性，三种水浸液均随着浓度的增加降低了生姜幼苗叶片内叶绿素的含量，而增加了生姜幼苗叶片的相对电导率和丙二醛含量。同时，三种水浸液均随着浓度的增加降低了生姜幼苗的光合参数（包括胞间CO2浓度、气孔导度、蒸腾速率及净光合速率）。 3. 三种生姜水浸液对所测六种土壤酶活性均产生了不同程度的影响，其中影响最大的是酸性磷酸酶和蔗糖酶，在10 g l-1 时就达到了显著水平，并且所有酶均有随着水浸液浓度增加而增大的趋势；相同部位的水浸液随着浓度的增加，细菌和真菌的数量呈增加趋势，而放线菌的数量呈减少趋势；三种生姜水浸液均随着浓度的增加降低了土壤中有机质的含量，加剧了土壤中硝态氮含量的积累，根茎水浸液对土壤有效磷、速效钾和铵态氮均显示出低浓度提高其含量而高浓度降低其含量的趋势，而茎和叶水浸液则随着浓度的增加均降低了其含量。 4. 与生姜单作相比，所有间作系统均在旺盛生长期和收获期不同程度地提高了土壤酶活性，同时也增加了土壤细菌数量及土壤微生物总数但不显著；所有间作系统在旺盛生长期和收获期均不同程度地影响了土壤真菌及放线菌数量（增加或减少），所有间作系统间的多样性指数差异不显著，除了旺盛生长期四种作物（生姜-大豆-四季葱-大蒜）的间作模式显著降低了多样性指数，其值仅为生姜单作的33.18%；生姜与大豆间作不仅提高了19.6%的生姜产量而且获得了较好的经济效益，并且，所有间作系统均显著抑制了生姜姜瘟病的发生。 5. 不同栽培模式不同程度地影响了收获期生姜的株高、分枝数、根茎产量及内在品质。其中处理2显著地促进了生姜的分枝（10.5%），同时处理2、3和4也促进了生姜的生长（株高分别增加了15.0%、11.4%和14.0%），并且这三个处理提高了生姜的产量；处理2和3能有效提高生姜块茎中维生素C（分别较单作生姜显著提高了3.29%和4.05%）、处理3显著提高了可溶性糖（8.2%）、姜辣素（4.6%）和蛋白质等有益物质的含量，降低硝酸盐有害物质的含量（处理2显著降低了14.0%），改善了姜块的外观和内在品质。并且，生姜与大豆间作具有最高的纯收入和产投比，分别较生姜单作提高了24.80%和8.8%。Recently, allelopathy has been more and more paid attentions by national and foreign scholars with profound research on reasons of crop replanted (continuous planted) obstacle. Ginger rhizome is valuable all over the world either as a spice or herbal medicine and ginger replanted obstacle is also paid attentions. Systematic research on ginger allelopathy will contribute to understanding and ultimate solving problem of ginger replanted obstacle. The effects of ginger aqueous extracts with different parts and concentrations on seed germination and early seedling growth of soybean and chive were studied in this article to testify that ginger existed allelopathy. Furthermore, ginger autotoxicity was also studied by pot experiment in greenhouse (namely research on effects of ginger aqueous extracts with different parts and concentrations on morphological indexes, physiological and biochemical indexes, photosynthesis, soil enzymes, soil microbial diversity and soil nutrients) to reveal mechanism of ginger degeneration and senescence, provide scientific basis for selecting appropriate intercropping species and put forward scientific resolvent for ginger replanted obstacle. The main results were as follows: 1. All aqueous extracts at all concentrations inhibited seed germination, seedling growth, water uptake and lipase activity of soybean and chive compared with the control, and the degree of inhibition increased with the incremental extracts concentration. The degree of toxicity of different ginger plant parts can be classified in order of decreasing inhibition as stem＞leaf＞rhizome. The results of this study suggested that rhizome, stem and leaf of ginger contained water soluble allelochemicals which could inhibit seed germination and seedling growth of soybean and chive. The rhizome is the main harvested part of ginger. The residue (mainly stems and leaves) of the ginger plant should be removed from the field so as to diminish its inhibitory effect. The main allelopathic components of three kind of aqueous extracts were as follows: Rhizome extract chiefly contained syringic acid and vmbelliferone and stem extract mainly contained frulic acid whose content was the highest (73.4 ug/g). The other six substances were detected except of frulic acid, but only contents of syringic acid, vmbelliferone and p-coumaric acid were higher. 2. Stem and leaf aqueous extracts of ginger with different concentrations significantly inhibited plant height, leaf numbers per plant and leaf area, and the degree of inhibition increased with the incremental extracts concentration. However, tiller number per plant of ginger seedling showed no significant difference. At the same time, ginger aqueous extracts also influenced biomass including under-ground biomass, above-ground biomass and total biomass (fresh weight) to a large extent. Under the same concentration, stem aqueous extract showed the mostly inhibitory effect on morphological indexes and biomass indexes of ginger seedling. Rhizome aqueous extract showed the leastly inhibitory effect and leaf aqueous extract was intervenient. Enhanced concentration of ginger aqueous extracts significantly reduced total chlorophyll content, accompanying with increases in memberane permeability (REL) and lipid peroxidation (MDA). Compared with the control, rhizome ginger aqueous extract of lower concentration (10 g l-1) increased the activities of major antioxidant enzymes (superoxide dismutase, SOD; peroxidase, POD; catalase, CAT; ascorbate peroxidase, APX) of ginger leaf tissue and higher concentration inhibited the activities of four antioxidant enzymes. However, stem and leaf aqueous extract inhibited the activities of four antioxidant enzymes with increase in concentration. Meanwhile, enhanced concentration of ginger aqueous extracts significantly reduced photo-parameters of ginger seedling (including CO2 concentration, stoma conductivity, net photosynthesis rate and transpiration rate). 3. Rhizome, stem and leaf ginger aqueous extract showed different effect on six soil enzyme activities, and acid phosphatase and invertase showed significant effect when aqueous extract concentration got 10 g l-1. Furthermore, six soil enzyme activities increased with increase in aqueous extract concentration. Bcterial and fungi number tended to increase while antinomyces tented to decrease with the increase in aqueous extract concentration of identical part. Ginger aqueous extracts reduced soil organic matter content with increased concentration, accompanying with NO3-—N accumulation in soil. Rhizome aqueous extract showed the same tendency for available P, available K and NH4+—N, namely lower concentration increased their contents in soil and higher concentration reduced their contents. While stem and leaf aqueous extracts reduced their contents with the increamental concentration. 4. All intercropping systems increased soil enzyme activities to different extent both at VGS and at HS compared to solo ginger. All intercropping systems increased the colony numbers of soil bacteria and total of soil microbe but not significantly either at VGS or at HS. All intercropping systems increased the colony numbers of soil fungi and actinomytes to a different extent (increase or decrease) both at VGS and at HS. For DI, difference between all cultivation patterns and S-G was not significant either at VGS or at HS except that G-S-C-G whose value was only 33.18% of S-G at VGS significantly decreased. G-S not only increased ginger yield by 19.6% but also obtained better economic benefit. Furthermore, all intercropping systems significantly inhibited occurrence of bacterial wilt of ginger. 5. Different cultivated pattern influenced plant height, tiller numbers, rhizome yields and intrinsic quality of ginger. Treatment 2 significantly facilitated tiller occurring (10.5%). Treatment 2, 3 and 4 promoted ginger growth (plant height respectively increased 15.0%、11.4% and 14.0%) and enhanced rhizome yields. Treatment 2 and 3 effectively increased vitamin C content (significantly increased 3.29% and 4.05% compared to solo ginger). Treatment 3 significantly increased contents of beneficial substances such as soluble sugar (8.2%), gingerols (4.6%) and protein. Treatment 2 significantly decreased contents of deleterious substance namely nitrate (14.0%) and improved appearance and intrinsic quality of ginger rhizome. Furthermore, treatment 2 (ginger/soybean intercropping) could obtain better economic benefit and showed the highest net income and ratio of benefit and cost whose values respectively increased by 24.80% and 8.8% compared to solo ginger.